As Google's digital book scanning project matures so it wants to start making money from it. The obvious way is to connect its preview service to retailers which sell the books, either electronic or dead tree versions.

A Google spokesman said: "We've consistently maintained that we're committed to helping our partners find more ways to make their books accessible and available for purchase. By end of this year, we hope to give publisher partners an additional way to sell their book by allowing users to purchase access to Partner Program books online. We want to build and support an digital book ecosystem to allow our partner publishers to make their books available for purchase from any web-enabled device - whether it's a PC, a smartphone, a netbook, or a dedicated reading device."

The big difference is that both the Kindle and iPhone demand dedicated content - you can't move downloaded books between the devices. Google has made much of its desire to see an open platform for books - which given its virtual monopoly on content is not surprising. Trying to repeat Google's five year digitisation project would be extremely expensive.

Google has already digitised some seven million books, it is also starting to digitise magazines.